In an ordinary telephone transaction performed between a terminal and a server via an automatic telephone exchange, a call is set up between a terminal and the server once the telephone exchange has identified the terminal (by its number which defines its physical connection and represents an account) so as to be able to charge the cost of the call to the account of the terminal, i.e. to the subscriber. There also exist cases where the cost of the call is charged to the account of the server ("800 numbers").
There also exist embodiments in which it is not the account of the terminal, i.e. of the subscriber, that is debited, but the account of a user. For example, a user having a memory card can call from a public telephone, and on the basis of information read from the memory card, the telephone exchange charges an account opened in the name of the user and identified by the memory card.
Document U.S. Pat. No. 4,933,966 relates to a system for verifying credit cards when setting up long distance calls. It does not relate to any transmission of identification data to a server after a call has been set up.
Document EP-A-0 494 530 relates to a system in which an exchange makes connections to various servers as a function of information coming from credit cards or as a function of an authorization code issued on the basis of data transmitted by a user. Billing is performed by the undertaking that manages the exchange. No identification data is transmitted to the server.
French patent No. 2 596 598 describes a very flexible system in which an exchange performs filtering operations by maintaining tables of authorized calls: the exchange enables calls to be set up either as a function of data relating to a terminal, or as a function of data relating to a user and carried by a data medium (badge, memory card, etc.).
In all those embodiments, the operations of determining which account to charge (terminal, user, server), or of authorizing a call, are independent of the server to which the terminal is to be connected once the call has been set up. More precisely, once a call has been set up between a terminal and a server in any of the above systems, either the server interchanges information with the terminal without knowing the identity of the caller (terminal or user), or else the server begins by performing a session for the purpose of determining whether the terminal or user participating in the transaction is indeed authorized to interchange information with the server. For example, when a bank customer calls the bank's server, the server identifies the user concerned because the user inputs information enabling the server to identify the caller (an access code). In other words, an interchange of information between the terminal and the server requires firstly that a call be set up under the authority of an exchange (public or private), and then once the call has been set up, it further requires a session during which the server asks the user for information (access code) telling the server that the user is indeed authorized to perform a transaction with the server.
The overall process therefore comprises two operations in which the terminal or the user partaking in the transaction is identified, firstly for the purpose of setting up the call (to determine an account to be charged), and subsequently for validating the interchange of information with the server (determining an account number, an access code, etc.).